Health Benefits of Garlic

Garlic is a handy herb to have around during
the winter holidays. According to most research to date, not only
does it help lower cholesterol, but it also apparently acts as a
natural antibiotic, fighting bacteria, fungi, and other
microorganisms. Some say garlic is as effective as penicillin,
tetracycline, streptomycin, and other prescription medications.

Sounds great, doesn’t it? But with the array of garlic products
on the market, not to mention the thriving belief that eating fresh
garlic is the only way to obtain its health benefits, consumers may
be bewildered when choosing their garlic preparation. Although the
jury is still out on which form is best and, indeed, a bit of an
industry “garlic war” has ensued, consumers can still make wise
choices. To that end, a little background information may be
helpful.

A Test of Time, a Body of Research

Ancient Egyptian and Chinese populations used garlic in various
ways, such as to fight infection and cure respiratory ­ailments.
Greek and Roman healers, including Hippocrates, all believed in its
ability to heal. Eighteenth and nineteenth century European
physicians explored its healing powers using then-new scientific
knowledge and prescribed it in much the same way as their ancient
predecessors.

But back then, garlic didn’t come in pills and researchers
didn’t use high-tech scientific tools to examine its every
particle. Today, however, it’s a different story. More than 2,500
research articles on garlic have been published in the past
century, with more than 1,000 of them appearing within the last two
decades, according to one author. The focuses of the research are
wide-ranging, documenting garlic’s potential not only to fight
infection, but also to prevent or delay the four leading causes of
death in the United States—heart disease, cancer, respiratory
disease, and liver disease.

Not all of the research has been positive, however. One report
appearing in the June 1998 issue of the Journal of the American
Medical Association put garlic’s ability to impact cholesterol
levels in question, although the findings were disputed by many
herb experts. They countered that the product used in the study had
been shown in previous tests to be less effective than other types
of garlic preparations.

Herb-watchers are particularly excited by what the research has
to say about garlic’s antibiotic potential. One reason for this is
that some pathogenic bacteria are becoming resistant to widely used
prescription antibiotics, which are either naturally occurring or
synthetically derived. Their strength was that they were developed
to attack specific kinds of harmful bacteria. But some bacteria
have developed their own ways of resisting attack, so the quest for
more naturally occurring, less specifically targeted antibiotics
has ensued.

Garlic is emerging as a clear alternative to prescription
antibiotics. Research outlines its potential to create an
inhospitable environment to a wide range of microorganisms,
including at least eight types of antibiotic-resistant bacteria and
some fungi, such as Candida, the microbe that causes yeast
infections, according to information provided by the nonprofit Herb
Research Foundation in Boulder, Colorado. Specifically, garlic
extract surpassed penicillin, ampicillin, doxycycline,
streptomycin, and cephalexin in fighting eight of nine strains of
Staphylococcus, ­Escherichia, and Proteus, according to the
foundation. Moreover, like the herb echinacea, garlic may possess
the ability to enhance immune function, making the body more
resistant to infection, some research shows.

What Makes it Work

Most researchers credit a compound in garlic called allicin for
the herb’s healing actions. Tests show that allicin inhibits the
enzymes that bacteria need to grow. One early report (it dates to
1952) states that the antibiotic effect of 1 mg of allicin equals
the antibiotic effect of 15 IU (10 micrograms) of penicillin.

Allicin is a sulfur compound that is ­created when garlic cloves
are crushed, cut, or chewed. Until the clove is broken down, it’s
odorless. But once the clove is opened, an amino acid called alliin
comes into contact with the garlic enzyme allinase, which quickly
transforms alliin into allicin and garlic begins to emit its
characteristic odor.

Research shows that if allicin doesn’t make it to the
intestines, it won’t do the body any good. Allicin may be destroyed
by stomach acids, so in order to get garlic’s full effect, the
compound must be protected. That’s why some garlic products are
“enteric-coated”—this coat shields the garlic product until it
reaches the intestine, where it is broken down and the prepared
garlic is released into the body. As for fresh garlic, some say
that the herb’s aromatic compounds are easily released from the
lungs and respiratory tract, so the benefit can be gained from the
fresh herb eaten alone or, more typically, prepared as a food
flavoring.

Still other studies indicate that more may be at work than
allicin. Researchers have identified about 200 compounds in garlic
and have focused primarily on the herb’s sulfur-containing
compounds, including S-allyl cysteine, or SAC, and S-allyl
mercaptocysteine, or SAMC. Some say these constituents also have a
role to play in the herb’s healing potential and shouldn’t be
overlooked; moreover, one manufacturer focuses on those two
compounds and disagrees that allicin holds any therapeutic
potential at all.

Researchers continue to search for the mechanism or mechanisms
by which garlic acts to help the human body. Meanwhile, industry
insiders are engaged in “garlic wars”—some designing their products
to protect allicin, others instead focusing on SAC and SAMC.

A Clove a Day?

Because so much research has concentrated on allicin, many
experts say that choosing a product that contains allicin may
ensure that you’ll receive the benefits garlic has to offer. Still
others acknowledge that more study is needed to determine which
garlic form is best—­allicin-packed, or allicin-empty—yet they go
further, saying that research may show that each preparation,
including fresh cloves, will have advantages that others don’t
have.

Until research defines garlic’s best form, perhaps the optimum
way to choose your garlic is to read about the suggested benefits
and pitfalls of each. And, as always, take note of any cautions
particular to your health condition and work with your health-care
provider to make sure that garlic is right for you. The dosage box
on this page offers a good starting point.

Dosage

How we know: More than 2,500 credible scientific studies have
established garlic’s potential to heal. At least nine
epidemiological studies show that garlic decreases the incidence of
cancer among those who consume it regularly.

Dosage: One medium-sized clove of fresh garlic chewed daily is
considered good preventive medicine; add raw garlic to cooked foods
just before serving to retain sulfur compounds. The German
Commission E suggests a 4-g daily dose of garlic. Processed garlic
products should deliver 5 g or more of allicin in a daily dose.
Allicin is an active constituent in garlic that most researchers
link to the herb’s health benefits, although some are disputing
this. One rule of thumb is to look for products that deliver 900 mg
of the powdered herb standardized to 0.6 percent allicin per 100
mg.

Cautions: Consuming moderate amounts of garlic
should be safe for most ­people.